1. Field of the Invention
The present invention concerns a baffle and reinforcement assembly which includes a carrier and a thermally expansible material designed for positioning in a cavity of a structural member to provide acoustic dampening and limited structural reinforcement. More particularly, the carrier mounts the thermally expansible material around the perimeter of the carrier to permit outward expansion and engagement with the surrounding structural member after activation.
2. Description of the Prior Art
The use of thermally expansible materials as baffles within cavities and to provide limited structural reinforcement has enjoyed increased popularity, particularly in the automotive field. The expansible materials, once activated, block acoustic transmissions through a structural member and provide, to a greater or lesser extent, structural reinforcement to the surrounding structural member. Examples of the use of such baffle assemblies are shown or described, for example, in U.S. Pat. Nos. 5,212,208; 5,266,133; 5,373,027; and 5,506,025. Because the relative expansibility of the material to a great degree affects its compressive strength, the greater the expansibility, the greater the acoustic performance but conversely the lesser the compressive strength and structural reinforcement capability.
However, there has developed a need for improved baffle assemblies which are lighter in weight, use less expansible material, and provide improved reinforcement to the surrounding structural member. Moreover, the particular configuration of the carrier and its manner of connection to the carrier may affect cost and ease of manufacture, the ability of the assembly to retain its shape during shipment, and the ability of the structural member to conform to and bond to the surrounding structural member after activation of the expansible material.
These and other objects have largely been met by the baffle and reinforcement assembly of the present invention. That is to say, the baffle and reinforcement assembly hereof provides a relatively easy to manufacture and simple to install assembly which inhibits acoustic transmissions through a structural member, provides limited additional reinforcement to the surrounding structural member, and effectively positions the expansible material to enter narrow creases formed in the structural member.
The assembly hereof includes a carrier element which is preferably molded of a synthetic resin material which is resistant to melting when exposed to elevated temperatures encountered in an oven in which the structural member is placed, and a thermally expansible material which is positioned around the periphery of the carrier and expands to engage the surrounding structural member. An attachment member, such as a clip, is provided on the carrier and preferably integrally molded therewith, the attachment member serving to locate and secure the assembly in position. The carrier serves not only to initially position the expansible material in proximity to the wall of the structural member, but also to direct it outwardly toward the structural member and into creases and recesses during expansion, so that expansion is principally directed to permit bonding with the interior surface of the surrounding wall of the structural member. The thermally expansible material is preferably injection molded in surrounding relationship around the carrier in a sequential molding process wherein the mold first receives the synthetic resin for the carrier and then the expansible material in successive infusions, or alternatively insert molded whereby the carrier is molded in a first mold and then transferred to a second mold with the expansible material molded therearound so that the carrier serves as a part of the second mold to provide the completed assembly. The carrier is preferably provided with a surrounding marginal rim which, in certain embodiments, has a base wall which supports and directs the expansible material outwardly, and supporting projections which retain the thermally expansible material thereon and provides a mechanical interconnection between the expansible material and the carrier.
The use of different projections at the margin of the carrier present a plurality of different possibilities for mechanically connecting the expansible material to the carrier. These include a substantially continuous T-shaped projection around which the expansible material may be molded, a plurality of intermittently positioned, circumferentially spaced projections around which the material is molded to present a woven connection, and circumferentially intermittent, alternately axially spaced projections which contain the expandable material therebetween. As used herein, xe2x80x9ccircumscribingxe2x80x9d or xe2x80x9ccircumferentiallyxe2x80x9d is not limited to circular or arcuate shapes, but rather to a path around the outer margin of irregular or polygonal shapes as well. The margin may also be configured as a U or Y shaped presenting two outwardly extending walls which receive the expandable material therebetween. The expandable material is advantageously formed as a continuous band without interruption around the perimeter of the carrier to ensure thorough and uninterrupted expansion all around the carrier after activation. The carrier and expandable material may also provide additional reinforcement to the structural member by the bonding of the expansible material to the wall of the structural member and the carrier and thus interconnecting the two around substantially the entire inner surface of the wall of the structural member and the entire periphery of the carrier.